Pulsing trailer lights

[ISUHawkeye]

I just finished wiring new LED tail lights onto my project trailer. the lights work great when the breaks are applied, and when the turn signals are activated, but when just the vehicle tail lights are on the lights pulse in a very dim constant flicker. any ideas as to why they are doing this??

[Verkstad]

LEDs are very rapid switching on and off, Therefore very prone to visible flickering if their power supply or ground connections are poor.
Also it might be an alternator problem on the truck. If the truck is not providing a steady smooth 12v, Of course the LEDs will flicker along with the supply voltage variations

Does the flickering remain constant as the motor is revved up?
Does it flicker if the motor is not running?? Or how about if a battery is connected directly to the lamps and nothing else...

If it turns out you suspect a supply problem, For diagnosis, Avoid using a digital voltmeter, it may not react fast enough to 'see' fluxuating voltage from the truck.
Aside from an osciloscope, An 'old school' needle type voltmeter can be a better choice to check for a voltage supply problem.

Good luck
Electricity is easy stuff.

[huskyfargo]

What do you drive?
My LED trailer lights do the same when my trailer is behind my LR3, my buddy's LR3, and my dad's Tundra. They did NOT flash, however, when I towed it behind my JK.
I've checked out everything. There are no problems with any of the ground connections or the power supply. As long as it doesn't bother you, there should be no problem with it.

[Martyn]

What do you drive?
My LED trailer lights do the same when my trailer is behind my LR3, my buddy's LR3, and my dad's Tundra. They did NOT flash, however, when I towed it behind my JK.
I've checked out everything. There are no problems with any of the ground connections or the power supply. As long as it doesn't bother you, there should be no problem with it.

Some vehicles need to sense a resistance from the trailer lights for them to function, as LED's provide very little resistance the vehicle computer can't sense the trailer. Seems to occur most often with Mercedes and VW vehicles. Putco makes a resister to solve the turn signal issue.

[skersfan]

Agree with Martyn, but I would check the truck side of the plug, with a needle type tester see if you have flickering there. If you do of course it is forward of the trailer. Besure you run the white wire to a ground on the trailer and insure it is clean bare metal where the ground is. I have started using bolts welded to the frame to provide a perfect ground. Do not use crimp connecter, solder the wires together.

I have not seen that problem, also as someone else said, take it directly to the battery and check it there, could be bad lights, but very doubtful.

Bob

[ISUHawkeye]

Thanks for all the responses. I am using a Landrover LR3. I just installed the lights and fresh wiring so I hope thats done right Maybe the truck is trying to hard.

[Hilldweller]

Do incandescent lights flicker on the circuit too?
If not, Martyn has most of the answer and the circuit could be pulsewidth modulated.
The resistor might work if its looking for EOL or a capacitor wired inline if its simply PWM.
Can you get your hands on an o-scope?